Tag Archive for: nitrogen

Understanding C3 & C4 Grasses

In the world of turfgrass, there are only two main grass types, cool-season grasses, and warm-season grasses. Both require photosynthesis to create their own food. Both perform differently in different heat situations, with cool-season grasses performing better in cool weather and warm-season grasses performing better in warm or hot weather.

But it isn’t enough to simply recognize this simple difference. To best care for each species of grass, it is important to know why each one is different and how they grow and produce carbohydrates through photosynthesis due to those differences. It’s far more important than most people realize.

 How Things Appear on the Surface

Cool-season grasses include species such as Kentucky Bluegrass, Tall Fescue, Creeping Bentgrass, and Ryegrasses to name a few. These emerge from dormancy quickly in the spring, grow rapidly, and slow down in late spring and summer. Growth is slowed or stopped by mid to late summer, especially if no irrigation is given. In the cooler weather of fall, growth picks up again but at a more moderate pace. Cool-season grasses can stay somewhat green all winter even though all growth has ceased.

Warm-season grass like Bermudagrass, zoysiagrass, centipedegrass, St. Augustinegrass, and others emerge from dormancy slowly as soil temps rise above 50 degrees, but full growth rate is not experienced until mid-summer. Growth rate slows in the fall and dormancy begins as temps fall below 50 or with the first heavy frost. Warm season grasses lose all of their chlorophyll in dormancy and will not green up again until it breaks dormancy in spring. In the deep south, some species of tropical grass will remain green all winter if the temps do not drop low enough to send the grass into dormancy.

C3 | C4

Each one has advantages and disadvantages. But below are the primary factors that shape why they grow this way and how to care for them. It is all centered around how they carry out photosynthesis.

The process of photosynthesis is carried out through a process of photosynthetic pathways. It sounds confusing, but it will become clear in a bit. The pathways have to do with the carbon compounds around which photosynthesis takes place. These two primary pathways are called the C3 and C4 carbon compound pathways.

C3 will always refer to the cool-season grasses and C4 always represent warm season grasses. There is no crossover. Therefore, scientists, when speaking of these grasses to other scientists or those educated in turf science will sometimes refer to these grasses as C3 and C4 grasses.

 Understanding C3 Grasses

Cool Season Grasses, or C3 grasses, are great at fixing CO2 at cooler temperatures. These are the temps they grow best in. However, at higher temperatures, above 90 degrees they are not as efficient. C3 grasses at higher temperatures have a hard time distinguishing between CO2 and O2. Remarkably, C3 grass can also catalyze the fixation of O2 which it does on equal or greater portions as CO2 in hot weather. When O2 is fixed it is called Photorespiration, and the result is lowered carbohydrate production.

When Photorespiration occurs the grass slows in growth and vigor and without water, the grass will often go dormant. It simply doesn’t have the energy to keep going.

A lot of people just don’t understand what is happening to their grass. They will assume the grass just needs more fertilizer and water. They will often over-fertilize with a high nitrogen mix in hopes of greening up the grass and restarting growth as in the spring. The result will often damage or kill the grass. This is because the grass simply cannot produce enough carbohydrates to match the nitrogen uptake and maintain growth. The fertilization is often accompanied by a lot of water or irrigation and for a while, the grass looks good. However, if the hot weather remains the victory is often short-lived. By adding too much nitrogen fertilizer, the nitrogen pushes the grass to grow at a time when it can’t handle it, thereby using stored nutrients in the roots since it cannot make enough carbohydrates to match the growth. As summer stress sets back in, it doesn’t have the reserves to draw on, and thinning or dieback often occurs. (Learn more about Organic Nitrogen in the Soil)

Therefore, it is good to remember that no matter how much nitrogen you apply in summer, C3’s will never overcome the grasses’ inability to produce the carbohydrates needed to grow in high heat. This is where experience comes in. It is possible to have a cool-season grass that is green all year, but the professional turf manager understands the balance between how much fertilizer to apply and how much irrigation and when not to push the grass. It takes a lot more irrigation for C3 to stay green in hot weather.

For general maintenance, C3 grasses can be fertilized by using low nitrogen or organic fertilizer including Turf Formula. The low nitrogen, slow release fertilizer will feed the plants what it needs, along with sufficient moisture, without pushing excessive growth that will damage the grass.

 Understanding C4 Grasses

Warm Season Grasses, or C4 grasses, are more efficient at CO2 fixation in high temperatures. This is because C4 grasses use a different enzyme than C3 and attach the CO2 to a different compound making up the 4 carbon compound. While it takes more energy for C4 to produce carbohydrates than C3, due to the extra steps involved, it does it without photorespiration and the end result is far greater carbohydrate production. 

As a result of the more efficient carbohydrate production, C4 grasses, depending on the grass variety and nitrogen needs, can be fertilized to maintain maximum growth in mid-summer or high summer heat. This will keep warm-season grasses growing through the summer months as long as water is available. If it is a low nitrogen grass, be careful that you don’t over-fertilize. Some grasses, such as Zoysia, are low N grasses and do not need more than 2 lbs of N per 1,000 sq ft/year.


C3 grasses are best grown in cooler environments. They are more efficient at fixing CO2 in cooler weather than C4 grasses. In addition, C3 grasses have a higher photosynthetic rate in shady conditions. This makes them more suitable for highly shaded, low light sites compared to their C4 relatives. (Learn more about the Science of Shade Grass Management Here

C4 grasses have a specialized photosynthetic process that focuses on CO2 in high heat. When C3 grasses are struggling to stay green, C4 grass is in its fastest growth of the year. C4 grasses in hot conditions have an increased Nitrogen Use Efficiency (NUE) and Water Use Efficiency (WUE). They are able to increase root mass and biomass in hot conditions when their cousins are starting to shut down.

 Special Situations

If you have turf-type tall fescue growing together with bermudagrass, you will have to make a decision on which you will maintain in summer. Bermudagrass requires up to 6 lbs N per 1,000 sq ft/year, double what fescue requires with much of it applied in the warmer months. This may damage or invite diseases in the fescue. If you hold back and do not fertilize in summer the bermudagrass can likely go dormant, especially with low moisture, due to not having the nitrogen to keep growing.

How to decide? Do you prefer the bermudagrass and overseed with fescue for wintergreen? Then fertilize through the summer. You can always add seed in the fall.  If you prefer the turf-type tall fescue, then do not fertilize in summer. It may take several years for the bermudagrass to die back and the fescue to dominate. 

To help the fescue dominate quickly, overseed in fall so it grows in thick by spring. Mow the grass at 2 -3 inches in spring before fescue green-up. The bermudagrass remains low since it won’t start growing until later in the year. Then set the blade at the mower’s highest height to shade the bermudagrass and weaken the grass as it is trying to emerge. Bermudagrass cannot grow in shade.

In contrast, if you prefer the bermudagrass, mow the grass low just before bermudagrass emergence from dormancy so the bermudagrass has plenty of sunlight. Fertilize and irrigate as needed to ensure maximum growth.

 How Can We Help?

Turf Formula® is a fantastic product that helps keep the grass functioning even in extreme or adverse conditions. University studies confirm Turf Formula®’s ability to increase fluid and nutrient uptake, provide more efficient photosynthesis, and lower sodium saturation in soils. Sodium competes with Potassium uptake. Potassium is essential for many plant functions, but stress relief in plants is what it is best known for.

Turf Formula® increases the plant available nutrients naturally. In studies at the University of Missouri/Columbia, naturally occurring beneficial soil microorganisms were increased by 3400% in 24 hours and by 5000% in 72 hours. In these trials, the samples included Super-Cal Calcium in with the Turf Formula®. These beneficial microbes perform a wide range of functions, including soil elements’ break down into nutrients the plants can use and to reduce disease pathogens.

Also, Mycorrhizae Fungi are significantly increased in the soil. Mycorrhizae are tiny organisms that colonize the plant roots forming a symbiotic relationship. These fungi draw nutrients and moisture back to the plant in exchange for small amounts of plant sugar. They can form long strands that act to extend the root’s reach. Plants in some parts of the country survive only because the Mycorrhizae are doing most of the work. All outdoor plants need Mycorrhizae to live and are naturally part of healthy soils. With healthy Mycorrhizae populations on root structures, plants can reach more nutrients than bare roots can achieve.

Russ James
AgriGro Turf Specialist

Call today for a free soil analysis to determine exactly what your lawn needs. 

Call Russ / Email Russ

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Lawn Care Academy, Russ James, Photosynthesis of Turf Grasses
Fundamentals of Turfgrass Maintenance, Photosynthetic Pathways Page 11, Dr. Nick Christians

Creating a Better World

 The Added Value You Gain That Makes All Your Hard Work Payoff

Turf maintenance and home lawn care is something we cannot take for granted. We have realized how much our health can be enhanced from the greenery around us. Having a home lawn and garden is not only nice to look at but is healthy as well. It gives us a sense of tranquility and order in a troubled world. Many take it for granted, not realizing that our plants and turf grass’s combined value far exceed any time or cost we invest in maintaining them. We were created for life in a green world, and we can’t live without it.

However, nature doesn’t merely make beautiful lawns on its own. If you have a lawn, I’m sure you have worked through some grass care problems. You are not alone. Having a beautiful green lawn will always be a work in progress and is a planned process from start to finish.

Take a look below at a few important facts about lawn grasses. You will see that all your hard work, whether you are in the professional turf maintenance industry or simply an avid home lawn care enthusiast, is an important part of creating a better world. 

 Did you know:

  1. An area of grass measuring 5000 sq. ft. in size produces as much oxygen as two 100 ft trees. That is roughly the size of an average front yard. An area of grass 650 sq. ft. in size can provide the daily oxygen needs for one adult. In the process of gas exchange, lawn grasses absorb large quantities of carbon dioxide from the air each day.
  2. Grass has an air conditioning effect on the environment. Roadways and sidewalks can heat up significantly higher than the surrounding air temperature while the adjacent grass will be cooler by at least 25 to 50 percent. A major complaint about artificial turf is that it absorbs heat. The temperature on these fields will often be 25 percent hotter than the air temperature in the stands. As a result, players have played in heat well into the 100s. Injuries also increase on artificial turf. Many stadiums have removed synthetic turf and replaced it with grass—the result: cooler fields, happier players, and fewer injuries.
  3. Performing good turf maintenance practices benefits us in many ways. A good covering of grass helps protect soil from erosion by holding it together through a complex network of roots. A good stand of grass slows water flow, giving it time to be absorbed and helping to recharge the water table. It also shades the soil and slows evaporation. (check out this Sports Field Maintenance article discussing the high demand on sports field managers)
  4. Lawn grass is a big part of nature’s air and water filtration system. Every year, enormous quantities of dust, pollution, and harmful gases are trapped and filtered out by grass blades and roots.
  5. A well-cared-for lawn can greatly increase a home’s value. This is a well-documented observation; manicured lawns add a sense of increased value to the property.
  6. Plants also add a sense of peace in a fast-paced world. Many have found relaxation in garden and lawn care. Experiments on the calming effect of plants were done on Russian Cosmonauts while in space. An area was built for green plants to be grown onboard the space station. Scientists notice that the Cosmonauts showed reduced stress, and their center of social activity always occurred near the plants. In inpatient care studies, hospital patients who were allowed to see and touch live plants felt better, healed faster, and went home sooner.
  7. Thick lawns and pastures are less conducive to weed growth. Poor grass care leads to problems. Many weeds are considered invasive, can attract problem insects, and are hard to control once established. Allowing invasive weeds to dominate harms the environment and is costly to remove.

Transforming grass into a beautiful landscape that is not only sustainable but healthy for you and your family, takes purposeful planning.   Often efforts can go against or deplete the healthy environment your working so hard to create. 

Looking for ways to use less fertilizer and other chemical inputs is important.

AgriGro® works to add life by working with nature and makes it possible to create a gorgeous landscape through our effective fertility program that is a cut above the rest.

Russ James
AgriGro Turf Specialist

Call today for a free soil analysis to determine exactly what your lawn needs. 

Call Russ / Email Russ

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Organic Nitrogen in Soil

While all nutrients are essential for plant life, Nitrogen(N) is the element that is required in the greatest amounts to maintain healthy and vigorous plant growth. It is also not very understood. As you will see, using organic sources for your plant nutrients is a lot different than just buying a bag of fertilizer. Let’s dive in to better understand how it works and the effects of organic nitrogen in the soil.

The interesting thing about nitrogen (in its natural form) is that it’s not derived from the soil like other nutrients, but comes from organic matter. Nitrogen released by soil microbes enters the soil as ammonia. Nitrifying bacteria convert ammonia to different forms, including nitrates, the form of nitrogen plants most readily use. If your soil is low in microbes, you will lose much of this ammonia to the air, lowering soil nitrogen levels. Therefore, it is essential to maintain your soil correctly. To help in this, Turf Formula is time tested and increases microbial levels and activity tremendously, which is vital to plant and microbial health. It helps deliver nitrogen and other nutrients faster and more efficiently for plants to use.

Consider how meadows, forests, and rangelands thrive yet do not receive supplemental nitrogen. They are dependent on a constant supply of organic matter to meet their nitrogen needs. In order for lawns and fields to maintain organic nitrogen in soils, organic matter comes from biodegradable materials such as grass clippings, shed roots, fallen leaves, decomposing twigs and branches, dead insect bodies, earthworm, insect, rodent and animal feces, and the like. Leaving grass clippings on the lawn can return 1 – 2 lbs of nitrogen per 1000 sqft each year back to the soil. 

Fertilizer bags always include three large numbers on the bag that represent Nitrogen, Phosphorus, and Potassium, in that order. It may have 0 for any of those nutrients if the bag contains none, but companies list them. Most of the fertilization programs professionally developed for turf are based on the amount of N needed on the grass for that time of year. It is equally important for organic lawn care. In turf science, it is said that a person skilled in Nitrogen management separates the true professionals from the average fertilizer user. Professionals are required to know this. 

Another interesting fact that runs contrary to popular belief is plants do not know or care where the nitrogen comes from. Whether through the breakdown of organic matter or by synthetic fertilizers, grass only knows it is nitrogen and will use it just the same.

 The Important Role of Soil Microorganisms to Grass Plant Health

While the grass doesn’t care about the nitrogen source, what about the soil? While it is true that some forms of nitrogen, such as ammonium, can harm some soil bacteria, it is only for a short time. As explained by the Texas A&M Agricultural Science Dept., soil bacteria immune to ammonium break it down into a plant-available nutrient. Then the harmed bacteria begin to recover rapidly. If the bacteria didn’t recover, the world would be in severe danger since 80% of the world’s ammonium is used as fertilizer.

To give you an example of how nature works, consider oil spills. Millions of spilled oil gallons can cause severe damage to birds, fish, microbes, and plant life. It upsets the whole balance of nature. Man tries his best to clean it up, but much of it is impossible to reach. 

This is where microbes come in. What is harmful to one microbe is like Swiss Chocolate to another. Oil digesting microbes can quickly breakdown the oil, and as that happens, the original microbes that were damaged by the oil soon return. This is what happened in the Gulf of Mexico during the BP spill. Within a relatively short time, the oil that pushed deep into the marsh was gone, and life sprang back. Life at the beach – crabbing, shrimping, and fishing – are now back to normal. 

If you have an organic lawn care service or strive to use organics as much as possible, maintaining your soil microbes is of supreme importance. There is nothing quite like Turf Formula® for home and sports turf, or FoliarBlend® for fields related to the most active and numerous microbial activity. University studies have shown Turf Formula® increases your natural microbial activity by up to 5000% in as little 72 hours. Soil microbes break down soil elements into nutrients plants can actually use, and it does it much faster. These microbes provide enzymes, amino acids, and other essential elements plants need for root development and overall plant health (read more on Sports Field Maintenance).

 Role of Nitrogen Inside the Plant

Magnesium is found inside the grass plant at the Chlorophyll molecule center, but three Nitrogen ions surround magnesium. Chlorophyll gives plants their green color and uses large amounts of nitrogen. Nitrogen is also found in amino acids, proteins, enzymes, nucleic acids, and more. It is an essential element for grass blade development, root and runner growth, photosynthesis, and other plant functions. Therefore, healthy grass is dependent on the correct amount of nitrogen availability. 

As already stated, soil microorganisms break down the organic matter and release back into the soil many different nutrients. The microorganism’s activity is related to temperature, with the greatest activity in the high heat of summer and winter being the slowest. As long as soil moisture is adequate, summer marks the fastest organic matter conversion back into nutrients.

To further challenge things, nitrogen is unstable in soil.  This is the primary reason soil tests often do not record Nitrogen levels, because it is so unstable, and levels quickly change. Suppose you are using organic forms of nitrogen. In that case, you need to keep a supply of organic material available to plants, especially from the start of the growing season, through the summer months and fall when microbes are at their highest activity levels. Organic matter can take many forms. Organic fertilizers, such as Milorganite, composted poultry litter, have all been used successfully. The latter generally have higher nitrogen levels than other manures at about 4% N. There are also “bridge products” that combine urea and other forms of N with the organic matter for increased nitrogen levels. 

Some companies make well-composted granulated manure fertilizers that are very safe. However, organic fertilizers cost more than non-organic. You can also use high-quality loamy topsoil or composts. 

Driving these points home, if you are doing organics, especially if you have an organic business, do not rely on nature alone. Your business depends on it. Keep track of organic matter levels via a soil test and the application rate of organic material afterward. If your soil is low in organic material, you will have low organic nitrogen levels in soil, and your grass will not be as green. As a result, your grass will show signs of chlorosis. You may not have enough nutrients to maintain the dark green color needed for healthy plants, and you will need to make organic additions or add fertilizers. 

Remember that chlorotic grass has lower disease resistance, lowered photosynthetic activity, and root development. It may go into dormancy to protect itself earlier when healthier grass would be green and thriving. You need to add Turf Formula to keep the microbial numbers high to convert soil elements and organic matter into nutrients.

If your soil is high in organic matter (6% organic matter is sufficient), then low maintenance turf can easily survive through the year. Places where clippings are left on the grass, such as home lawns, low traffic parks, cemeteries, amenity grasslands, etc., can often survive without nitrogen applications. Suppose your soil is lacking in organic matter. In that case, there may not be enough nitrogen to sustain healthy and vigorous plant life. You will need to add nitrogen in the form of fertilizers or add organic matter through top dressing with loamy topsoils or composts. Sports turf has higher standards, and nutrient levels will need to be closely monitored (check out the article on why Organic Matter Matters).

 How Much Topsoil Should I Get

Another question to consider is, “how much topsoil will it take to cover my front yard with 1/2″ deep of good loamy soil?” 

If purchased in large volumes, it often will come in cubic yards. To get an idea of how much that is, first imagine a child’s toy blocks. They often have letters on them, and you can stack them. Place nine blocks on the floor in a solid square three blocks wide and three blocks long. Then stack two more sets of blocks exactly like it one top of each other. Now you have 27 blocks in three rows of three on every side. If those blocks were one ft square (each block is 12″ on each side), you would have 27 of them, which would equal a cubic yard. That is a lot of dirt.

 Where to begin:

To answer how many cubic yards of topsoil you need, you will first need to know how many square feet is in your yard. So if your lawn is 50 ft X 25 ft, you have 1250 ft².

Since we are talking in fractions of 1/2″, we first need to convert the fraction into feet to calculate the volume of material. Here’s how we do that:

1/2 in depth = 1 ÷ 2 = .5 inches or half an inch **(if you needed 3/4″ deep of topsoil the math would be 3 ÷ 4 = .75 inches**)

Now divide: .5 in ÷ 12 in/ft² = .041 ft²

 Then to get the volume of material needed for 1/2″ deep:

Front Yard Sqft = 1250 ft² X .041 ft² = 51.25³ (The 3 reprepresents “cubic feet”)

You will need 51.25 cubic feet to topsoil to cover it 1/2″ in-depth.

 Now, if you will need to order it in cubic yards:

If one cubic yard = 27³ cubic feet, then how many cubic yards are 51.25³ cubic feet?

Divide: 51.25³ ÷ 27³ = 1.89 Cubic Yards. You will need just under two cubic yards. You can round it up to two if you like to make it easier for the guy loading it.


You can apply Turf Formula®, or Turf Formula® mixed with SuperCal® Liquid Calcium, right over the top of the soil.  In a test conducted by the University of Missouri where Turf Formula® and SuperCal® were applied, Brown Patch disease pathogens were reduced by 35% within 72 hours over the control. Many beneficial microbes feed on pathogenic microbes, and this action may be enough to keep most diseases from becoming problems (check out the study here and AgriGro’s prebiotic impact on soil diversity and richness).

The use of Turf Formula® has helped control Take-All Root Rot, Cedar Apple Rust, Pythium Blight, as well as other diseases.  Cedar Apple Rust on apple trees was controlled entirely the year it was tested. The following year the Turf Formula® application was withheld to see what would happen, and the cedar-apple rust came back. Turf Formula® is not a fungicide, but by increasing beneficial microbes, many bacteria and protozoa have one primary function: to find and kill pathogenic microbes. Turf Formula® significantly increases fluid uptake, promotes significant root growth, and aids in more efficient photosynthesis. 

AgriGro products have become a valuable, time-tested resource for organic and non-organic lawn care professionals, used on golf courses and lawns around the country and around the world. If you haven’t tried it, now’s the time.

Russ James
AgriGro Turf Specialist
Call Russ / Email Russ

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Lawn Care Academy Turf Specialist, Russ James
Fundamentals of TurfGrass Management – Dr. Nick Christians
The Mathematics of Turfgrass Maintenance – Dr. Nick Christians
Texas A & M Turfgrass Resources